<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
     .box{
        width: 5em;
        height: 5em;
        background-color: aqua;
     }

    </style>
</head>
<body style="font-size: 30px;">
    <div class="box">
       
    </div>
</body>
</html>